The present invention relates generally to a seat construction, and more particularly to a construction which is especially suitable for vehicle seats and the like. In its broadest aspect, the invention relates to adjusting arrangements.
Many seats, especially those in automotive and other vehicles, are now being constructed so that the back can be raised or lowered to the preference of a user. Such seats are provided with arrangements which permit the back to be pivoted relative to the actual seat member and to be arrested in a selected position. These arrangements have a handle, in form of a turnable knob or the like, which turns to release and to reengage the arrangement, and they usually have a brake sleeve in which there is located a helical spring that engages the inner surface of the sleeve in frictional relationship and has opposite ends engaging an input member that is turnable by means of the knob, and an output member, both of these members being turnably mounted coaxially with reference to the sleeve. The purpose of the spring is to prevent undesired relative displacement of the seat member and the backrest member, which may occur -- especially in the case of automotive vehicles -- as a result of vibrations, shocks and the like, even though the cooperating gears of the arrangement may be of the self-locking type.
The spring in these prior-art arrangements cooperates with portions of the input and output member. Since the end portions of the spring are not in constant contact with these portions of the input and output members, the prior-art arrangements must undergo an idling movement, that is they must traverse a certain distance when the arrangement is actuated by turning the knob, before the output member is engaged and taken along by the input member (which is being turned by the knob) to effect relative displacement between the backrest member and the seat member of the seat. The play which causes this idling movement is to some extent determined by the fact that it must be possible to stress the helical spring in a sense reducing its diameter so as to decrease the braking effect which it has, for the duration of the displacement of the backrest member relative to the seat member. However, the play is determined to a much larger extent by manufacturing tolerances which must be relatively liberal in order to permit economic manufacturing conditions. If these manufacturing tolerances were to be tightened, the degree of precision required during the manufacture would be so high as to make the parts in question too costly.
On the other hand, this idling movement described above is often found bothersome by a user, particularly if because of it the user must change his grip on the handle one or more times in order to obtain the desired adjustment in the position of the backrest member relative to that of the seat member. This is especially true when the handle is configurated as a turnable knob.